1. Field of the Invention
The present invention generally relates to a projection apparatus, and particularly, to a projection apparatus that adjusts the position of projected image.
2. Description of Related Art
With the development of science and technology, various projection apparatuses have been widely used in various situations, such as briefings, lectures, theaters, audio-visual teaching, interactive teaching, family theatre sets and the like. In order to meet the requirements of users, the profile design of a projection apparatus will trend to be more beautiful and small, and adjustment of the projection angle of the projection apparatus may be implemented by configuring an adjusting leg.
Referring to FIGS. 1A and 1B, a projection apparatus 100 includes a casing 110, a projection lens 120, two lifting legs 130 and an adjusting leg 140. The casing 110 comprises a leading end 112, a back end 114 and a bottom 116, and the projection lens 120 is assembled on the leading end 112 of the casing 110. The two lifting legs 130, for example, are respectively configured on the two sides of the bottom 116 of the casing 110 near the leading end 112, and the adjusting leg 140, for example, is configured on the middle position of the bottom 116 of the casing 110 near the back end 114. Referring to FIG. 1C, when using the projection apparatus 100, users may change the top angle (α) of the projection lens 120 and the tilting angle (β) of the projection apparatus 100 by respectively adjusting the two lifting legs 130, so as to change the position of the image projected by the projection apparatus.
However, the lifting legs 130 of the projection apparatus 100 are generally made of screws or racks, and the lifting leg 130 made of screws generally comprises comparatively small screw pitch so as to have the function of fine tuning, thus more time is consumed for adjusting the projection angles (the top angle α and the tilting angle β) of the projection apparatus 100. Furthermore, the lifting leg 130 made of racks generally comprises comparatively large screw pitch so as to have the function of coarse tuning, thus the lifting leg 130 is not adjusted to a preferred position when the projection angles (the top angle α and the tilting angle β) of the projection apparatus 100 is adjusted.
In order to resolve the problems mentioned above, an adjusting leg having both screws and racks is provided in the U.S. Pat. No. 6,302,543B1 allowing the lifting leg of the projection apparatus to have the functions of coarse tuning and fine tuning. Referring to FIG. 2, the lifting leg 210 of the projection apparatus 200 includes a first adjusting apparatus 212 and a second adjusting apparatus 214. In the conventional technique, the first adjusting apparatus 212 is comprised of racks to have the function of coarse tuning, and the second adjusting apparatus 214 is comprised of screws and connected to the first adjusting apparatus 212 so as to have the function of fine tuning
However, the lifting leg 210 of the projection apparatus 200 as shown in FIG. 2 simultaneously comprises the functions of coarse tuning and fine tuning, the structure thereof is comparatively complex, and the fabrication cost is higher. Furthermore, when users pack the projection apparatus 200, the lifting leg 210 is generally accommodated in the casing 220, thus the height of the lifting leg 210 need to be readjusted during each use of the projection apparatus 200, and the operation is comparatively inconvenient.